Substation circuits



y Feb. 19 1924.

K; s. .JoHNsoN v SUBSTATION CIRCUITS Filed Jan. l0 1921 Patent Feb. 19, 1324..

KENNETH S. JOHNSON, OF JERSEY CITY, NEW JERSEY, 'ASSIGNOR TO WESTERN ELEC- TRIO COMINY, INCORPORATED, OF-NEW'YORK, N. Y., .A CORPORATION 0F NEW" YORK.

SUBSTATION CIRCUITS.

Application led January v10, 1921. Serial No. 436,304.

To all whom it may concer/n,

Be it known that I, KENNETHS. JOHN- soN, a citizen of the United States, residing at Jersey City, in the county of Hudson,

State of New Jersey, have invented certain sirable to use a substation circuit in which. the instruments are actually or effectively 1n.

series with each other. It is an object of this invention to connect the telephone instruments eectively in parallel with respect to a line and to arrange the connections so that maximum eliiciency may be had.

In the preferred 'form o1c the invention the receiver is connected across the line without the intervention of inductive means. The transmitter, however, Vis connected to the line by Vmeans of a two-winding auto-trans- Jformer for the purpose of kproperly adjust ing the impedance of the transmitter to that of the line. f rIhe invention will be more fully understood from'the following detailed description and claims taken in connection with the accompanying drawing, in which each of Figs. 1 to 9 inclusive, represents diagrammatically an arrangement in which the instruments are connectedeffectively in parallel with respect to the line and one or both of the instruments are connected to the line through a two-winding auto-transformer; Figs. 10 and 11 represent respectively, two ways oi supplying current to a system employing the circuit of Fig. 4.

Referring to the drawings by reference characters, each of the circuits shown comprises an auto-transformer having windings A and B. In Fig. 1, a transmitterT andv a receiver R are connected in parallel across the winding-B, while line L is connected across both windings A and NB. In Fig. 2,

the line and the transmitter are connected across winding B, while the receiver is connected across both windings. In Fig. 3, the line and the receiver are connected across winding B, and the transmitter is connected across both windings. In Fi 4, the line and the receiver are connecte across both windings while the transmitter is connected across winding B. In Fig. 5, the line and `the transmitter are connected across both windings and the receiver is connected across winding B. In Fig. 6, theline is connected across winding B, and the transmitl ter and receiver are connected in parallel across both windings.- In Fig. 7, the-line is connected across both windings, the receiver is connected across winding A and the transmitter is connected across winding B. In

,F ig. 8, the line is connected across winding A, the transmitter across winding B, and the receiver across both windings. In Fig. 9, the line is connected across winding A, the receiver across winding-*B and the transmitter across both windings'.

In designing a substation of the types shown herein, the impedance of the set should equal` that of the line to which it is to be connected, and under good line conditions when receiving, the received energy vshould be dissipated equally in the `receiver and the transmitter. 'Av discussion of the principles involved in two-way signalling in telephone substations will be found in Campbell Patent No. 1,254,474, dated January 22, 1918, and a more complete discussion including the circuits herein disclosed will be found in a paper entitled Maximum output networks for telephone substation and repeater circuits, by George A. Campbell and Ronald M. Foster, read before' the American Institute of Electrical Engineers in New York, February 19, 1920, publishe in the transactions of that organization for 1920, vol. 39, Part I, page 231. Figs. 1 to o s above stated, the value of y should be the value of 1.

9 herein are shown in the above paper in Fig. 9, in the following order, circuits with elements effectively in parallel, Nos. 32, Se, 33, 39, 4o, 33, 35, 33 and 37.

Taking the circuit shown in Fig. l as an example, the design i'ormul for the set impedance Vand the energy ratio may be obtained as follows:

Assume an electromotive force e acting in the line L, and currents having their directions and values indicated in the drawing.

Let L, T, R, A., B and M represent the values of the impedances of the line, transmitter, receiver, and Vthe sel-t impedances fngs and B, and their mutual impeda'nce respectively.

A Let. i

and

By Kirchhois laws We obtain by going around the mesh containing L and R ELL-nia (1) by going around the mesh containing A, Band R by going around the mesh containing B and T irri"(iRJrrmLieeHrRJfiLm/rzo (3) Bearranging equations (l), (2) and (3):

TLL-|-TR(-R)|TT(O)V:6

i..(Alema-M)+iR A+B+2M+RH mei-mio (5) Solving these equations simultaneously, We

inliiiitelyl large as compared with T, We get Y Tt Willbe, noted that the impedance of the ITZT :if-M: g/B. this resolves to R B+M y:T LDB-@iii (15) [R (B -l- M) PT ge +Mw) [Aefewmme +'r)]+ [Bifirmzme +M); of Zs and from the value of TL as given'in the equation (7) substation as given in equation 13 is in the forni of Ha, fraction, the numeratorl of which involves the product of the receiver` and the transmitter impedances and the denominatorinvolves their sum, thus indicating thatthe telephone instruments are et ec'tiVe-lyu in lparallel for received currents. jlhile Vin actualfpractice the value of Bis not infinite, still if properlyd-esigned, its value is'large asV compared with the impedance of the transmitter and very little current loivs'serially through the receiver and transmitter. y

From equations (8) and (9) and the detinition or" y, We obtain:

unity for maximum efficiency. Conditions such as line noise may make it preferable to give this ratio a valuesomevvhat greater than l. This invention, accordingly, is not limited to cases Where' y has precisely The design formulae for the other circuits shown herein may be obtained by methods similar to the above. In every case it will be found that the impedance formula is of a form similar to equation 13 showin that the instruments are effectively in para lel.

In Fig. 10, is shown an adaptation of the circuit of Fig. 4 which has been found useful as an operators circuit in fire alarm systems in which the operators circuit is connected to a large number of substation circuits simultaneously. Since the substation circuits are connected in parallel, the impedance of the line as seen is considerably lower than that of the average telephone line. The impedance of the operators cir cuit however, can easily be designed to be correspondingly low, since the instruments are effectively in parallel. The receiver R is connected in series With a condenser 15 across the line. With respect to alternating currents, the transmitter T is connected across winding 8 just as in Fig. 4. 18 represents a common battery which is employed for energizing the transmitter of the substation circuits (not shown), which may, for example, be the residence telephone circuits of the individuals belonging to a local fire company. This battery is also employed to energize the transmitter T of the operators circuit. The direct current circuit comprises the transmitter T, the battery 18 and the retardation coil20, which is designed to have a sufficiently high direct current resistance to cut down the voltage to the proper value for the transmitter. In one installation where a twenty-four volt common battery was employed, the winding of coil 2O had a direct current resistance of 165 ohms. The condenser 22 is provided to prevent the direct current from being short-circuited around the retardation coil. The inductance 20 is substantially an open circuit for talking currents and the condenser 22 is of negligible impedance for such currents, so that from the alternating current standpoint the circuit resolved to that of Fig. 4.

In Fig. 11 is shown the operators circuit, disclosed in the application of W. P. Andrick and J. I'I. Dahl, Serial No. 419,413, filed October 25, 1920, when in the condition in which ythe switches have been operated to connect the operators circuit to'a plurality of substation circuits. This circuit is similar to that of Fig. 10, except that the retardation coil 20 and condenser 22 are omitted and the common battery is divided into two parts 25 and 26, so arranged that the two parts are in series with respect to the line, but that a fraction only of the total voltage applied across the line is effective in producing current in the transmitter T.

The circuits shown herein are similar to the three winding auto-transformer circuits shown in my copending application Serial No. 195,364, liled October 8, 1917, for Telephone substation sets, in that the telephone instruments are effectively in parallel.

`What is claimed is:

1. A substation circuit comprising a transmitter and a receiver, connections from said instruments to a line, said instruments being connected eectively in parallel with each other with respect to signaling currents from said line, said connections comprising a two-winding auto-transformer between at least one of said instruments and said line, and a battery connected to send current through said line, said last mentioned instrument being energized by direct current from said battery.

2. A substation circuit comprising a transmitter and a receiver, connections from said instruments to the line, said instruments being connected eectively in parallel with each other with respect to signaling currents from said line, said connections comprising a two-winding auto-transformer between said transmitter and said line, and

a battery connected to send current through` said line, said transmitter being energized by direct current from said battery.

3. A substation circuit comprising a transmitter and a receiver, connections from said instruments to a line, said instruments being connected eectively in parallel with each other with respect to signaling currents from said line said connections com-y prising a two-winding auto-transformer said line and said receiver being connected across both windings of said transformer, and said transmitter being connected across one of said windings.

4. A substation circuit comprising a twowinding auto-transformer, a receiver and a line connected across both windings of said transformer, the transmitter being connected across one of Vsaid windings, a common battery adapted to send current out on said line, and connections for energizing said transmitter through said battery.

5. A substation circuit comprising a twowinding auto-transformer, a transmitter,

KENNETH S- JOHNSON.

and a receiver, said transformer serving to l 

